The jack bean lectin, concanavalin A (Con A), binds saccharides containing glucose or mannose residues in a manner analogous to an antigen-antibody reaction. The lectin precipitates glycoproteins containing the appropriate sugar residues and selectively agglutinates tumor cells. Although Con A is widely used as a probe to reveal alterations in the composition and organization of tumor cell membranes, little is known about the molecular properties of the agglutinin that are responsible for its binding and agglutinating activities. In order to provide insights into possible modes of interaction of the lectin with carbohydrate determinants of normal and transformed cells, it is necessary to understand the molecular properties of the protein associated with its carbohydrate binding specificity. We have recently described the use of 13C nuclear magnetic resonance (NMR) techniques for determining structural and dynamic information of the molecular interactions between monosaccharides and Con A. The objectives of this proposal are to extend our previous studies using similar NMR techniques to: (1) investigate the binding of other mono- and oligosaccharides to Con A, (2) to characterize the molecular nature of the saccharide combining site of the protein, and (3) to investigate the relationship between the metal ion binding properties of Con A and its saccharide binding activity.